Brief Answer:
Likely to be due muscle stiffness - wrong posture.

Detailed Answer:
Hello,
Thanks for posting your query.
This looks like a positional anomaly. The upper back ache is a result of muscle spasm which in itself is a protective mechanism body develops so that the back avoids abnormal posture. For pain to go, it takes not only rest (on a comfortable bed) but also avoidance of particular positions (during work, rest or recreation).
The feeling of burning sensation and nausea may be related to proper supplements for a few days will help.
If the back pain is unbearable take medications/ pain killers or muscle relaxants prescribed by your physician. And if it has been long standing illness visit your orthopaedician and clinically-radiologically establish a diagnosis to commence definitive treatment.
I hope this answers your query.
In case you have additional questions or doubts, you can forward them to me, and I shall be glad to help you out.
Wishing you good health.
Regards.
Dr. Praveen Tayal.

---